1. Field of the Invention
The present invention generally relates to a radio (wireless) terminal apparatus such as a mobile vehicle telephone and a portable telephone, and a mobile communication system such as a mobile (vehicle) telephone system and a portable telephone system with employment of this radio terminal apparatus. More specifically, the present invention is directed to battery power saving techniques under call waiting states of radio terminal apparatuses for constituting this sort of mobile communication system.
2. Description of the Related Art
In general, a radio (wireless) terminal apparatus for constructing a mobile communication system performs a location registering operation when a power supply is turned ON, and thereafter operation of this radio terminal apparatus is brought into a call waiting state. Then, under this call waiting state, a battery power saving operation is carried out.
As such a conventional radio terminal apparatus, for instance, Japanese Laid-open Patent Disclosure JP-A-Showa 63-316942 opened in 1988 discloses "RADIO TELEPHONE APPARATUS". It should be noted that the disclosed radio telephone apparatus will be referred as "first conventional technique" hereinafter in this specification. Referring now to FIG. 1A, FIG. 1B and FIG. 2A to FIG. 2D, a description will now be made of this radio terminal apparatus related to the first conventional technique.
FIG. 1A schematically represents the arrangement of the mobile communication system according to the first conventional technique. This mobile communication system is arranged by a radio (wireless) base station control apparatus, a plurality of radio base station apparatuses, and a plurality of radio (wireless) terminal apparatuses. FIG. 1B is a block diagram for showing the arrangement of the radio terminal apparatus for constituting this conventional mobile communication system. This radio terminal apparatus is arranged by a radio (wireless) signal transmitting/receiving unit 1, a speaker 2, a microphone 3, an input/output apparatus 4, a control unit 5, a memory unit 6, and an antenna 9. A detailed description of each of these elements will be explained in connection with a preferred embodiment.
FIG. 2A to FIG. 2D are explanatory diagrams for explaining the summary of battery power saving operation executed in the radio terminal apparatus of the first conventional technique. More specifically, FIG. 2A is a timing chart for representing a notification signal group transmitted from the radio base station control apparatus via the radio base station. FIG. 2B is a timing chart for showing an ON/OFF condition of the power supply supplied to the radio signal transmitting/receiving unit 1 (simply referred to as a "signal receiving circuit") of the radio terminal apparatus. FIG. 2C is another timing chart for showing the above-described notification signal group, in which the scale of the abscissa in FIG. 2A is reduced. FIG. 2D is another timing chart for representing the above-described ON/OFF condition, in which the scale of the abscissa in FIG. 2B is reduced at the same reduction ratio of FIG. 2C.
Under call waiting state of the radio terminal apparatus, the turn-ON/OFF operation of the power supply of the signal receiving circuit is controlled in a predetermined time period (this time period is referred as the "battery power saving period"). As shown in FIG. 2B, within 1 battery power saving period, the power supply of the signal receiving circuit is turned ON in a 1/4 section of 1 time period, whereas this power supply is turned OFF in a 3/4 section of 1 time period. In other words, a ratio of the turn ON/OFF of the power supply of the signal receiving circuit is 1:3. Then, while the power supply of the signal receiving circuit is turned ON, a confirmation is made as to whether or not the call signal to the own radio terminal apparatus is produced. This call signal contains the notification signal and the calling signal (will be explained later).
As shown in FIG. 2C, the radio base station control apparatus transmits the notification signal group to the radio terminal apparatus via the radio base station apparatus, for instance, at an interval of 5 minutes in order to register the location. This notification signal group is constituted by a plurality of notification signals identical to each other, and these notification signals are transmitted in the asynchronous mode within the above-described battery power saving period. Also, a total number of notification signals contained in the notification signal group is determined in order that the transmission time of the notification signal group becomes longer than the battery power saving period. Such a notification signal overflowed from the battery power saving period is called as a "notification signal of +a.alpha.". As represented in FIG. 2A, in this first conventional technique, 4 pieces of the notification signals are transmitted within 1 battery power saving period, and further one piece of the notification signal is transmitted as the "notification signal of +.alpha.". In other words, the radio base station control apparatus transmits 5 pieces of the continuous notification signals via the radio base station apparatus in the interval of 5 minutes.
As indicated in FIG. 2B, in the radio terminal apparatus, the power supply of the signal receiving circuit is turned ON under control of the control unit in the 1/4 section of the battery power saving period. As previously explained, the timing when this power supply is turned ON is not synchronized with the notification signal sent from the radio base station control apparatus via the radio base station apparatus.
It should be understood that when a call is issued to the radio terminal apparatus managed by the radio base station control apparatus, this radio base station control apparatus transmits the calling signal group via the radio base station apparatus irrelevant to the above-described transmission timing of the notification signal group, as shown in FIG. 2C. Similar to the above-described notification signal group, this calling signal group is constructed of 5 pieces of continuous calling signals (not shown).
The reason why either the same notification signals or the same calling signals are continuously transmitted 5 times in this first conventional technique is given as follows. That is, the power supply of the signal receiving circuit is turned ON only in the 1/4 section of the battery power saving period and further the battery power saving period is not synchronized with the send timing of either the notification signal group or the calling signal group. Thus, in order to firmly receive either the notification signal or the calling signal while the power supply of the signal receiving circuit is turned ON, either one piece of the notification signal or one piece of the calling signal is outputted in addition to either four pieces of the notification signals or four pieces of the calling signals, which correspond to the battery power saving period.
The battery power saving ratio is 75% in the case that the radio terminal apparatus of the first conventional technique is operated under call waiting state. Assuming now that the ON/OFF ratio of the power supply of the signal receiving circuit is 1:4, the battery power saving ratio is increased to 80% when this radio terminal apparatus is operated under call waiting state. However, in this case, either the same notification signals or the same calling signals are required to be continuously transmitted 6 times, so that the load given to the radio base station control apparatus is increased.
Another conventional radio terminal apparatus is disclosed in "JTC (AIR)/95.06.08-033R3 [SP-3418]", section 6.4.1 "Alerting Protocol" on pages 69-74. This disclosed convention radio terminal apparatus is called as "second conventional technique".
FIG. 3A to FIG. 3F are explanatory diagrams for explaining the summary of battery power saving operation executed in the radio terminal apparatus of the second conventional technique. More specifically, FIG. 3A is a timing chart for representing the calling signal transmitted from the radio base station control apparatus via the radio base station, and FIG. 3B is a timing chart for showing the ON/OFF condition of the power supply of the signal receiving circuit of the radio terminal apparatus. FIG. 3C is another timing chart for showing the above-described calling signal, in which the scale of the abscissa in FIG. 3A is reduced. FIG. 3D is another timing chart for representing the above-described ON/OFF condition, in which the scale of the abscissa in FIG. 3B is reduced at the same reduction ratio of FIG. 3C.
The circuit arrangement of the mobile communication system and the circuit arrangement of the radio terminal apparatus contained in this mobile communication system, according to this second conventional technique, are identical to those of the first conventional technique shown in FIG. 1A and FIG. 1B. As represented in FIG. 3A and FIG. 3C, the calling signal is transmitted from the radio base station control apparatus via the radio base station apparatus in 1 second time period. FIG. 3E shows a frame structure of the calling signal within the 1-second time period. As apparent from FIG. 3E, this signal transmitting period is constructed of 400 frames (BOB-399). When the location registering operation is performed, an operation of the radio terminal apparatus is synchronized with that of the radio base station control apparatus (radio base station apparatus), and the block used to transmit the calling signal is allocated. The radio base station control apparatus transmits the calling signal at the timing of the block allocated to the radio terminal apparatus during the location registering operation by using 1 frame through 3 frames every 1 second via the radio base station apparatus. For the sake of simple explanations, it is assumed that the calling signal is transmitted every 1 second by using 1 frame.
Even when no calling signal is received at such a radio terminal apparatus corresponding to a certain block, the radio base station control apparatus sends out the dummy data to this radio terminal apparatus by using 1 frame. In the case that a call signal is received at a certain radio terminal apparatus, the radio base station control apparatus continuously transmits the call signal via the radio base station apparatus at the timing of the block allocated to this radio terminal apparatus only the number of times of transmission (2 times to 5 times) which are determined as the system information.
As a result, assuming now that when a location of a certain radio terminal apparatus is registered, for example, a block 3 (B3) is allocated as a calling block, the power supply of the signal receiving circuit is turned ON at the timing of the block 3 only one time per 1 second during 1/400 second (minimum) to 3/400 seconds (maximum) under control of the control unit 5 in the radio terminal apparatus. FIG. 3F represents such a condition that the power supply of the signal receiving circuit is turned ON at the timing of the block B3 within the respective sending period (1 second).
In such a case that the predetermined number of times of transmission is equal to, for example, 4 times, when a calling signal is received by such a radio terminal apparatus allocated to the block 398 (B398), as indicated in FIG. 3E, a calling signal for calling this radio terminal apparatus is continuously sent 4 times every 1 second at the timing of the block B398 by the radio base station control apparatus.
The battery power saving ratio when the radio terminal apparatus of this second conventional technique is operated under call waiting state becomes 99.25% (=(400-3)/400) in such a case that, for example, the calling signal is sent out by using three frames.
There is a great difference between the first conventional technique and the second conventional technique. That is, in the first conventional technique, the calling period of the radio base station control apparatus is not synchronized with the time period during which the power supply of the signal receiving circuit employed in the radio terminal apparatus is turned ON, but is synchronized with the time period in the second conventional technique. As a consequence, in the response waiting process operation for the calling operation, the calling signal is resent when the time out of the timer set to a predetermined value is occurred in the first conventional technique, whereas the calling signal is continuously transmitted irrelevant to the response in the second conventional technique.
A first problem occurred in such conventional technique, the duration time of the battery employed in the radio terminal apparatus is short. This first problem is caused by such a fact that the power of this battery is consumed even when the radio terminal apparatus is operated under call waiting state. In a certain condition, the user of this radio terminal apparatus cannot recharge this battery for a long term.
In such a case, when the remaining power quantity of this battery becomes zero while the user continues the telephone communication, this telephone communication is interrupted.
A second problem of the conventional technique is caused by such a fact that there are great possibilities that the calling signal cannot be surely received. That is, when the reception signal field strength of the control channel is low (weak), if only one calling signal is sent, then there are high possibilities that the reception of this calling signal fails because of the fading phenomenon.
Furthermore, Japanese Laid-open Patent Disclosure JP-A-Heisei 4-273695 discloses "MOBILE COMMUNICATION APPARATUS" as the related art. In this mobile communication apparatus, the location registering operation of the changed radio base station is carried out only when the location registering demand transmitted from the radio mobile station in a predetermined time period is received by the respective radio base stations, and the reception signal field strength of this demand signal can be detected as such a highest reception signal field level continuously received preselected times. However, in this conventional mobile communication apparatus, the power supply of the signal receiving circuit is not turned ON/OFF in response to the reception signal field strength level.
Also, Japanese Laid-open Patent Disclosure JPA-Heisei 1-177223 opened in 1990 discloses "MOBILE RADIO COMMUNICATION APPARATUS". This mobile radio communication apparatus is applied to the radio communication system arranged by that a plurality of base stations are arranged at random; the channels are allocated to the respective base stations whose channels are different from those of the adjacent base stations; the mobile radio communication apparatus owns the transmitting/receiving means for the respective channels; and then the radio communications are established with the base stations within the service areas of the respective base stations by using the channels allocated to the relevant base station. This mobile radio communication apparatus is arranged by the field strength measuring reception means, the comparing means, and the control means. The field strength measuring reception means sequentially receives the channel signals outputted from the respective base stations to thereby acquire the field strength measurement output. The comparing means compares the measurement output from this field strength measuring reception means with the field strength output of the reception signal derived from the above-described signal transmitting/receiving means, and produces the switching output when the measurement output of the field strength measuring reception means exceeds the field strength output of the reception signal of the signal transmitting/receiving means. The control means continuously outputs the measuring channel switching command used to sequentially switch the reception channels of the field strength measuring reception means, and switches the transmission/reception channel of the signal transmitting/receiving means to such a reception channel of the field strength measuring reception means upon receipt of the switching output from the comparing means. In accordance with the conventional mobile communication apparatus, this mobile communication apparatus can continuously access to such a base station where the reception signal field strength is the highest level. However, in this mobile communication apparatus, the power supply of the signal receiving circuit is not turned ON/OFF in response to the reception signal field strength level.
Further, Japanese Laid-open Patent Disclosure JP-A-Heisei 4-251370 opened in 1992 discloses "POWER SUPPLY FOR PORTABLE TYPE INPUT/OUTPUT APPARATUS". This power supply for the portable type input/output apparatus is arranged by the secondary battery corresponding to the power source; the charge/discharge detecting unit for discriminating the charge operation from the discharge operation based on the current flowing direction of the secondary battery to transmit the discrimination data; and the A/D converting unit for measuring the charge voltage and the discharge voltage of the secondary battery to A/D-convert these measured voltages into the corresponding digital data. Further, this power supply is constituted by the RAM for temporarily storing the digital data derived from the A/D converting unit; the ROM for previously storing the control software; the CPU for executing the data process operations based on the digital data stored into the RAM and also the data derived from the charge/discharge detecting unit under control of the control software stored in this ROM; the display unit for displaying the remaining battery power quantity and the battery lifetime based on the data process result of the CPU; and the connection unit for connecting the main body of the portable type input/output apparatus so as to supply the electric power of the secondary battery. However, this conventional portable type input/output apparatus power supply does not execute the battery power saving operation in response to the remaining power quantity of the secondary battery, but merely displays the remaining electric power of the secondary battery.
Also, Japanese Laid-open Patent Disclosure JP-A-Showa 58-103238 opened in 1983 discloses "RADIO APPARATUS". This conventional radio apparatus is arranged by the transmitter and the receiver having the power supply control unit. The transmitter transmits the calling signal during a preselected time period after the calling switch is turned ON. The receiver is intermittently operated only within a short time period in such a time period shorter than the above-described preset time period, and the electric power is supplied to the demodulating circuit unit having the relatively slow response characteristic in response to the power application within this short time period. Thereafter, the electric power is applied to the other circuit units such as the low frequency amplifier having the quick response characteristic. This radio apparatus further includes the power supply voltage detecting circuit for detecting the power supply voltage, and the receiver with such a power supply control unit having the following functions. That is, when the power supply voltage detected by this power supply voltage detecting circuit is low, the start timing of the power supply voltage is advanced. Conversely, when the detected power supply voltage is high, the start timing of the power supply voltage is delayed so as to vary the power supplying period for the demodulating circuit unit. As previously explained, this conventional radio apparatus controls the start timing of the power supply voltage to the demodulating circuit unit so as to vary the power supplying period. In contrast, a radio terminal apparatus (will be explained later) according to the present invention owns such a different technical idea. That is, the time duration during which the power supply voltage is applied is varied by changing the power supplying period.
Also, Japanese Laid-open Patent Disclosure JP-A-Heisei 4-345330 opened in 1992 discloses "MOBILE RADIO APPARATUS". This mobile radio apparatus employs the means for intermittently operating the signal reception system when the call is received, the means for controlling the time period of this intermittent reception operation, and the means for detecting the field strength during the intermittent signal reception. Then, when the detected field strength is low, the time period of the intermittent signal reception operation is prolonged to reduce the power consumption. To the contrary, in the radio terminal apparatus according to the present invention, when the detected field strength is low, the time period of the interrupted signal reception operation is shortened so as to surely receive the calling signal.
Also, Japanese Patent Publication JP-B-Showa 59-12055 published in 1984 discloses "MOBILE COMMUNICATION SYSTEM". In this mobile communication system, the paging call sent via the saving control channel from the base station is received/detected by the calling signal receiving circuit to which the electric power is supplied from the power supply in a predetermined time period, and the electric power of the power supply is supplied from the telephone battery saving circuit to the telephone transmitting/receiving circuit in response to this paging call reception, or the on-hook operation of the transmitting/receiving device. The designation information of the communication channel sent from the base station via the connection channel is received/discriminated to set the communication channel. However, this conventional mobile communication system does not describe the battery power saving technique in response to the remaining power quantity of the power supply.
Also, Japanese Laid-open Patent Disclosure J-PA-Showa 62-160830 opened in 1987 discloses "SELECTIVE CALLING SIGNAL RECEIVER". This selective calling signal receiver is arranged by that in the radio receiver having the battery power saving circuit, for receiving/processing the selective calling signal, the synchronization monitoring means is employed which includes the detecting means for detecting the error of the selective calling code contained in the selective calling signal, and the control means for controlling the battery power saving circuit in response to the error detection signal derived from this error detecting means. However, in this conventional selective calling signal receiver, such a power saving operation cannot be carried out in response to the remaining power quantity of the power supply as executed in the inventive radio terminal apparatus.
Further, Japanese Laid-open Patent Disclosure JP-A-Heisei 4-211529 discloses "BATTERY POWER SAVING METHOD OF PAGING SYSTEM". This conventional battery power saving method of the paging system is featured by that in the paging system using the paging signal for sending the sync code and the calling signal subsequent to the preamble signal, there are employed the first battery power saving means for executing the battery power saving operation in the short time period until the first preamble signal is detected, and the second battery power saving means for turning OFF the power supply under such a condition that when the preamble signal is once detected and the subsequent sync signal is detected, from the end of the calling signal until this preamble signal of the paging signal is detected, namely from the end of this paging signal, this power supply is turned OFF. However, this conventional battery power saving method of the paging system cannot carry out such a battery power saving operation in response to the remaining battery power quantity as executed in the inventive radio terminal apparatus.
Furthermore, Japanese Laid-open Patent Disclosure JP-A-Heisei 4-304043 opened in 1992 discloses "RADIO SELECTIVE CALLING RECEIVER". This conventional radio selective calling receiver is equipped with the radio signal unit, the decoding unit, the calling signal detecting unit, and the notifying unit. Further, the zone detecting unit and the power supply control unit are employed. This zone detecting unit detects whether the present location of the receiver is located within the signal receivable zone, or outside the signal receivable zone in response to the individual calling signal. In the power supply control unit, the first time interval and the second time interval longer than this first time interval are set, and the intermittent power supplying operation of the power supply unit 6 is selected as the first time interval or the second time interval in response to the output from the zone detecting unit. However, this conventional radio selective calling receiver cannot perform such a battery power saving operation in response to the remaining power quantity of the power supply as executed in the inventive radio terminal apparatus.